B0550

Code

Generic B — Body

Body Control Module Internal Fault

Brand: Generic

Type: B — Body

Views: UK: 16 EN: 32 RU: 25

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Page language: EN

Causes

BCM internal component failure (processor, memory, power regulation)
Corrupted or failed BCM firmware / software
Low or unstable supply voltage to BCM (battery, charging, parasitic draw)
Damaged or corroded connectors, pins, or wiring at the BCM
Water intrusion or physical damage to BCM module
Voltage spikes or improper jump-starting / aftermarket electrical modifications

Symptoms

Multiple body systems inoperative or intermittent (door locks, interior lights, exterior lamps, wipers)
Instrument cluster or dash warnings indicating BCM error
Loss of remote/keyless functions or alarm faults
Intermittent or permanent CAN bus communication errors with other modules
Electrical accessories working erratically or not at all
Possible excessive battery drain or no-crank situations if BCM controls power distribution

What to check

Connect a scan tool and record all stored and pending DTCs and freeze-frame data
Verify battery voltage (with engine off and cranking) and charging system output
Inspect BCM connector(s) for corrosion, bent pins, water intrusion, or damage
Check fuses and relays related to BCM power and accessories
Verify good chassis and battery ground connections at BCM and vehicle ground points
Check for other communication codes (U-codes) that indicate network issues

Signal parameters

Primary supply voltage to BCM: nominal 12–14.5 V (engine running) and >= 11 V at rest
Ignition-switched supply present when key ON (voltage present on IGN feed pin)
Ground continuity:
CAN bus idle voltages: CAN_H ~2.5 V, CAN_L ~2.5 V (differential ~0 V idle, ~2 V dominant)
Module wake/sleep currents: should match spec in service manual (excessive mA indicates fault)
Communication: periodic CAN/LIN messages originating from BCM when awake (check with scan tool/scope)

Diagnostic algorithm

Read and record all DTCs and freeze-frame data with a capable scan tool; note any U-codes or multiple B-codes.
Verify battery/charging condition; charge battery if low and recheck codes after stable voltage.
Visually inspect BCM and connector: look for corrosion, water intrusion, melted plastic, or heat damage.
Check fuses/relays supplying BCM and test continuity of power and ground circuits to the module.
Verify CAN/LIN communication: use scan tool to see if BCM responds; use scope or meter to check bus voltages.
Perform wiggle and back-probe tests on BCM harness while watching live data for intermittent faults.
If wiring/power/ground and network are normal, attempt a soft reset per manufacturer procedure (battery disconnect or BCM sleep), then clear codes.
Check for and apply any BCM software updates or reflash the module per service information.
If reflash fails or internal faults persist and all external checks are good, consider module replacement and reprogramming to vehicle configuration.
After repair or replacement, clear codes, perform relearn/programming procedures, and road test to confirm fault resolution.

Likely causes

Failed internal electronics inside BCM (most likely if no external wiring faults found)
Poor power/ground connection to BCM (common and easily checked)
Corroded connector or pin/pad damage at the BCM connector
Software corruption requiring reflash or replacement
Network communication fault causing BCM to set internal-fault code

Fault status

⚠️ Status

Internal fault detected in Body Control Module — verify power, grounds, communications and module integrity; reflash or replace BCM if internal failure confirmed.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1-3 hours